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The Influence of Facial Characteristics on the Relation between Male 2D:4D and Dominance

  • Jan Ryckmans,

    Affiliation Faculty of Economics and Business, Research Center for Marketing and Consumer Science, KU Leuven, Leuven, Belgium

  • Kobe Millet ,

    Affiliation Department of Marketing, VU University Amsterdam, Amsterdam, Netherlands

  • Luk Warlop

    Affiliations Faculty of Economics and Business, Research Center for Marketing and Consumer Science, KU Leuven, Leuven, Belgium, Department of Marketing, BI Norwegian Business School, Oslo, Norway

The Influence of Facial Characteristics on the Relation between Male 2D:4D and Dominance

  • Jan Ryckmans, 
  • Kobe Millet, 
  • Luk Warlop


Although relations between 2D:4D and dominance rank in both baboons and rhesus macaques have been observed, evidence in humans is mixed. Whereas behavioral patterns in humans have been discovered that are consistent with these animal findings, the evidence for a relation between dominance and 2D:4D is weak or inconsistent. The present study provides experimental evidence that male 2D:4D is related to dominance after (fictitious) male-male interaction when the other man has a dominant, but not a submissive or neutral face. This finding provides evidence that the relationship between 2D:4D and dominance emerges in particular, predictable situations and that merely dominant facial characteristics of another person are enough to activate supposed relationships between 2D:4D and dominance.


Animal and human studies suggest that prenatal exposure to testosterone influences both brain development and behavior [1]. As it is difficult (in animals) or even impossible (in humans) to directly measure prenatal exposure to testosterone levels, the second to fourth digit ratio (shortly 2D:4D) has increasingly been adopted as an indirect biomarker for prenatal testosterone exposure. Much evidence suggests that lower 2D:4D indicates a higher level of prenatal testosterone exposure [2, 3, 4, 5]. During the last decade abundant evidence has accumulated for the profound impact of prenatal testosterone exposure, indexed by 2D:4D, on personality traits, e.g. Sensation Seeking [6], trait physical aggression [7], implicit power motivation [8] and dominance [9], as well as on actual behavior, e.g. responses to infidelity threat [10], athletic prowess [11], and agreeableness towards women [12]. In the present paper we focus on the relationship between 2D:4D and dominance.

In biology, the capacity of 2D:4D to serve as a biomarker of dominance is well documented. The relationship between 2D:4D and dominance has been found at the species level: the competitive chimpanzee has a lower 2D:4D than the less competitive bonobo [13], and generally there is evidence that species with more competitive social systems have lower 2D:4D ratios [14]. Within species, low 2D:4D is associated with higher dominance rank in primates such as rhesus macaques [15] and baboons [16, 17].

In human research, the evidence for a similar relationship is mostly circumstantial. Several findings suggest that low 2D:4D reveals the need to achieve, to win, or to outdo others [18]. Indeed, low 2D:4D is related to success in sports such as professional football, rugby, rowing, endurance running, slalom skiing, and fencing [11, 19, 20, 21]. Similar relationships between 2D:4D and success have been observed in completely different settings: low 2D:4D predicts success among high frequency financial traders [22], increased academic performance in male dentistry students [23] as well as better performance on a cognitive reflection task [24] and a Java programming course [25].

These findings, linking 2D:4D to (success in) competitive activities do at least suggest that 2D:4D may serve as a biomarker for dominance in humans as well. But evidence for a direct relationship between 2D:4D and dominance is mixed. Some studies do find a significant relationship with personality measures of dispositional [9], and aggressive dominance [26] but a similar number of studies does not observe any relationship [27, 28]. Interestingly, Manning and colleagues [9] ran a large scale study to assess the relationship between a dominance measure and 2D:4D among more than 150.000 participants, and found a correlation of r = -.03 between the dominance measure and both male and female 2D:4D. This relationship is weak, even after taking into account that due to the higher level of error in self-measured 2D:4D the actual correlation would be about three times higher [29]. Summarized, the literature illustrates a remarkable paradox: whereas 2D:4D is predictive for performance in sports, financial markets, and cognitive tasks that suggest the quest for dominance, there is no strong support for a direct linear relationship between 2D:4D and personality measures of dominance.

To unravel the paradox it is instructive to look, as other authors have done, at how context effects may modulate the relation between 2D:4D and behavioral outcomes [18, 30]. For instance, impulsiveness (as measured by financial discounting) appears only negatively related to male 2D:4D after a (experimentally manipulated) defeat in a competitive setting, but not after victory [31]. To the extent that impulsiveness is suboptimal behavior in the long run, this finding is at least consistent with the idea that low 2D:4D men are more dominant and therefore may have more difficulties in accepting this particular situation. Similarly, it has been shown that the relationship between 2D:4D and aggression is modulated by the setting in which the relationship is measured. Low 2D:4D predicts aggressive behavior only after watching a violent video [32, 33] and only predicts retributional responding following provocatively unfair offers [34]. These findings fit very well with findings on the relation between circulating testosterone levels and dominance-seeking behavior. In humans, measurements of testosterone, in blood or saliva, strongly predict status seeking behavior when an individual’s status is threatened, but not in the absence of a threat [35, 36]. In non-human primates testosterone relates to dominant and aggressive behavior only when the status hierarchy is unstable and dominance battles are possible [37, 38]. It has been proposed that testosterone only predicts dominant behavior when circumstances activate our “dominance” system, which is comprised of motivational and attentional processes that prepare us to take actions that allow us to maintain or enhance our social status [39]. Consistent with this perspective, particular facial cues are able to activate dominant responses in high testosterone individuals: after testosterone administration, eye contact—which may be seen as a display of dominance—is maintained longer when confronted with angry faces than with happy faces [40], even when these faces are masked. Given the observation that facial cues seem to be sufficient to activate a dominance related behavioral repertoire, we focus in the present study on the impact of facial characteristics on the relation between 2D:4D and dominance.

Facial cues have been shown to be important predictors for a wide range of social decisions, such as whether to trust an interaction partner in a trust game, whether to convict those who stand trial, or whether to vote for a specific candidate in an election [41, 42, 43]. These outcomes are at least partially driven by the fact that people promptly and unreflectively draw inferences about others’ intentions and personal dispositions on the basis of facial information and subsequently act upon these inferences [44]. In the case of the facial emotional expression of anger, the social signal is quite clear: the sender clearly communicates to the interaction partner the intention of a dominance clash. Such a social challenge seems to provoke retaliation in dominant individuals, while submissive and anxious individuals are more likely to give in [45]. Furthermore, these findings suggest that mere facial emotional expressions are able to activate one’s own dominance system and by doing so influence actions.

Interestingly, the dominance system also might be activated by facial cues irrespective of emotional content. In fact, Oosterhof & Todorov [46] identified trustworthiness and dominance as two dimensions that are sufficient to account for more than 80% of the variance in holistic neutral face evaluation. Research regarding specific stable morphological characteristics in emotionally neutral faces, especially those relating to facial maturity and masculinity, provides additional evidence that these cues trigger inferences related to dominance hierarchies and influence evaluations about not only physical strength [47], but also personal dispositions in relation to dominance and aggression: Variation, for instance, in “baby facedness”, characterized by stable morphological facial cues such as round faces and big eyes, influences perceptions of fitness and submissiveness [48]. Variation in facial width-to-height ratio in emotionally neutral faces predicts estimated propensity for aggression in others [49, 50]. More direct evidence that dominance-related facial cues activate the dominance system comes from neuroscientific findings that these cues preconsciously activate neural systems related to status and aggression [51, 52].

Considering that exposure to dominant-related facial cues can activate the dominance system and the observation that testosterone only predicts dominant behavior when circumstances “activate the dominance apparatus” [39], we propose that exposure to dominant facial characteristics enables the relation between 2D:4D and dominance to emerge. Specifically, we hypothesize that 2D:4D is more strongly related to dominance after exposure to dominant than to neutral or submissive facial cues.


Hundred-thirty-one heterosexual male participants between 18 and 38 years of age (90,8% (n = 119) Caucasian, 3.1% (n = 4) Chinese, 6.1% (n = 8) non-Chinese Asian) participated in this experimental study, which was approved by the Social and Societal Ethics Committee of the KU Leuven, and provided informed consent in writing. After reading the instructions participants completed the Social Value Orientation Slider Measure [53]. In this resource allocation paradigm, participants were asked 6 times how they would distribute monetary resources between themselves and another anonymous person. The responses to the six items, differing in joint payoff options, allow for the calculation of a person’s social value orientation. While the original paradigm does not include any information about the anonymous interaction partner, we slightly adapted the paradigm to allow for a between-subjects manipulation of facial dominance: when introducing the task to participants, we displayed a facial image of this hypothetical interaction partner, and we also showed this face before the six resource allocation decisions between the participant and the interaction partner. Participants were randomly allocated to a condition in which they were shown an emotionally neutral face with either submissive, neutral or dominant characteristics and reassured that mutual anonymity would be guaranteed. We manipulated the facial characteristics by using faces generated by a computer model that allows manipulation of facial dominance [54]. Oosterhof & Todorov’s extensively validated model [46] provides assurance that stimuli are well standardized, and specifically attuned to parametrically manipulate the facial dominance cues and associated trait dimension required for this research [46, 51, 54, 55]. The faces from this database were originally created using FaceGen 3.2 software [56]. We used two facial identities from Todorov’s dominance database [57] to enable generalization of the results. These were randomly allocated to participants. Three levels of dominance were chosen (-3, 0 and +3 SD on a normally distributed dimension) for each facial identity to determine submissive, neutral or dominant faces (see S1 Fig). This specific procedure allows to manipulate facial dominance characteristics while keeping other visual features of the interaction partner constant. As a result any difference in response can only be due to these changes in specific facial characteristics. Further, although imaginary, this particular setting and the decisions involved in this paradigm are assumed to come as close as possible to a real setting while keeping all other potential confounding factors controlled. Immediately after this task, participants were asked to complete the 11-item dominance scale of the International Personality Item Pool [58], a scale that focuses strongly on self-aggrandizing aspects of dominance and contains items like “I impose my will on others” and “I try to outdo others”. Participants responded to each item on a seven point scale from disagree (1) to agree (7). Finally, participants’ right hand was scanned to measure finger lengths. Participants placed their hand palm on the glass plate of a scanner and we ensured that details of major creases could be seen on the scans. Finger lengths were measured by two independent raters from the ventral proximal crease to the tip of the finger by means of the freeware program Autometric developed by DeBruine [59]. Finger lengths were measured from the bottom crease when there was a band of creases at the base of the digit [60].


Prior to the main analyses we calculated the Intraclass Correlation coefficient (ICC = .985), averaged the highly correlated 2D:4D measurements of both raters and used this average in our statistical analysis. We also tested the reliability of the dominance scale. Two items (“Hate to seem pushy” and “Demand explanations from others”) showed problematic factor loadings (< .30) in a PCA and were omitted from further analyses. The revised 9-item dominance scale resulted in a Cronbach’s Alpha of .74. After averaging the items of the dominance measure, we conducted a general linear model (GLM) analysis with facial dominance condition (collapsed across facial identities), 2D:4D (mean-centered) and the interaction between both as independent variables and with the averaged score on the International Personality Pool dominance scale as dependent measure. As predicted, we observed a significant interaction effect between 2D:4D and facial dominance condition, F (2, 125) = 3.50, p = .033, η2 = .053, indicating that 2D:4D is negatively related to dominance in the dominant face condition (r = -.37, p = .01), but not in the neutral (r = .09, p = .58) or submissive (r = .06, p = .68) face conditions (see S2 Fig). No other effects turned out to be significant (all F’s < 2.2 and p’s > .12). Average age across conditions was comparable across conditions (21.8 years, 21.0 years and 21.1 years in the dominant, neutral and submissive conditions respectively), as was the average 2D:4D score (0.953, 0.956, 0.953, respectively). Prior research showed that Blacks and Chinese have lower 2D:4D than Caucasians [61]. In this study no Blacks participated, and only 4 participants were Chinese (3 in the dominant, none in the neutral and 1 in the submissive condition). Without the Chinese participants, the interaction between 2D:4D and facial dominance condition remained significant (F(2, 121) = 3.87, p = .023, η2 = .060). The results are also robust across participant age. When age was added as a covariate, the interaction remained significant (F(2,124) = 3.48 p = .034, η2 = .053, while the main effect of age was insignificant (F(1,124) = 0.013, p = .91, η2 = .00).


Our findings provide new insights in different domains. First, our pattern of results sheds some light on earlier inconsistent findings with regard to whether 2D:4D can predict self-rated dominance. 2D:4D does reliably relate to actual and perceived facial features typically considered male and dominant [62, 63, 64], which implies the potential to activate the dominance system in interaction partners. Behavioral findings in both animal and human research also suggest that 2D:4D may serve as a biomarker of dominance [1325]. Still, prior research only observed weak relationships between 2D:4D and explicit dominance measures [9, 26, 27, 28]. Our results resolve the inconsistency by taking into account that activation of the dominance system through particular contextual cues may predict when relationships between 2D:4D and dominance related behavior actually emerge [3034]. The contexts that have been described to activate the dominance system are perceived as challenges or provocations, such as experiences of competition with other men in areas like territory formation, dominance disputes, or mate acquisition and guarding, or even challenges to one’s honor or reputation [65]. These environmental contingencies seem to heighten the importance of one’s position in the status hierarchy and trigger men’s striving for dominance [35, 36]. In line with this literature, we provide evidence in our study that merely activating thoughts about a presumed interaction that involves the distribution of resources with a dominant (but not a neutral or submissive) looking man may lead to the emergence of the relation between 2D:4D and explicit dominance measures. The present pattern of results accentuates that ignoring context will hide the existence of stable–but situated—relationships between 2D:4D and other variables. Second, whereas previous research regarding facial characteristics mainly focused on how facial cues guided trait inferences about the interaction partner [48, 49, 50, 51], our experimental results demonstrate that stable morphological facial cues related to dominance are able to influence inferences regarding one’s own biologically rooted personality predispositions with respect to dominance striving. Future research should investigate how this translates to a range of ecological distributive behaviors, common–for example–in buyer-seller interactions or organizational settings. Another path for future research may focus on the mechanism behind the effect. Some evidence suggests that low 2D:4D relates to high testosterone production after aggressive and/or physical challenges [66, 67, 68]. Given that testosterone especially predicts dominance when the dominance system is activated [39] these circulating testosterone levels may explain why a relationship between 2D:4D and dominance especially emerges when men are exposed to dominant opponents.

Based on the findings in the current study, we suggest that across many domains emotionally neutral dominant facial cues will activate the dominance system and increase vigilance, that is, men may be prepared for competition when meeting a dominant other. This vigilance may be captured in the relation we observed between 2D:4D and dominance after hypothetical interaction with a dominant other. This does not mean that mere interaction with a dominant other always leads to competitive action, as dominant others do not necessarily have to fight for dominance. Indeed, if facial dominance cues represent an interaction partner’s capability to inflict harm, rather than their intent [46], mental preparation might be an adaptive response until other cues clarify which action is appropriate. In view of the literature regarding the ‘challenge hypothesis’ [35, 36, 65], an interaction partner’s capability to inflict harm might just alert a man to a potential challenge or provocation, and hence merely lead to a state of mental preparedness. In line with findings relating to responses to angry faces [45], a potential challenge by a dominant looking individual seems to provoke mental preparation for dominance-striving in individuals with a biologically dominant nature, while individuals with a biologically submissive nature are more likely to mentally prepare for yielding or withdrawal. Being mentally vigilant and prepared for a potential dominance clash is adaptive for dominant men as it allows them to strategically optimize their behavior to increase their chances to maintain or enhance status. It is equally adaptive for submissive men as it potentially allows them to respond in a way that avoids the interaction to evolve into a harmful one. As Louis Pasteur once said: ‘Chance favors the prepared mind’; it might just be that men in the face of latent conflict with substantial costs and benefits mentally prepare for the appropriate response in order to optimize their chances of success.


The present study provides experimental evidence that male 2D:4D is related to a dominance measure after (fictitious) male-male interaction when the other man has a dominant, but not a submissive or neutral face. This finding provides evidence for the idea that the interaction with a dominant other activates the dominance system which leads to the emergence of a negative correlation between 2D:4D and dominance.

Supporting Information

S2 Fig. Relationship between right hand 2D4D and dominance by facial condition.


Author Contributions

Conceived and designed the experiments: JR KM. Performed the experiments: JR. Analyzed the data: JR KM. Contributed reagents/materials/analysis tools: JR KM. Wrote the paper: JR KM LW.


  1. 1. Hines M. Gender development and the human brain. Annual review of neuroscience. 2011; 34: 69–88. pmid:21438685
  2. 2. Manning JT, Scutt D, Wilson J, Lewis-Jones DI. The ratio of 2nd to 4th digit length: a predictor of sperm numbers and concentrations of testosterone, luteinizing hormone and oestrogen. Human Reproduction. 1998; 13(11): 3000–3004. pmid:9853845
  3. 3. Talarovičova A, Krškova L, Blažekova L. Testosterone enhancement during pregnancy influences the 2D:4D ratio and open field motor activity of rat siblings in adulthood. Hormones and Behavior. 2009; 55(1): 235–239. pmid:19022257
  4. 4. Zheng Z, Cohn MJ. Developmental basis of sexually dimorphic digit ratios. Proceedings of the National Academy of Sciences. 2011; 108(39): 16289–16294.
  5. 5. Auger J, Le Denmat D, Berges R, Doridot L, Salmon B, Canivenc-Lavier MC, et al. Environmental levels of oestrogenic and anti-androgenic compounds feminize digit ratios in male rats and their unexposed male progeny. Proceedings of the Royal Society of London B: Biological Sciences. 2013; 280 (1768): 20131532.
  6. 6. Hampson E, Ellis CL, Tenk CM. On the relation between 2D:4D and sex-dimorphic personality traits. Archives of Sexual Behavior. 2008; 37(1): 133–144. pmid:18075733
  7. 7. Bailey AA, Hurd PL. Finger length ratio (2D: 4D) correlates with physical aggression in men but not in women. Biological psychology. 2005; 68(3): 215–222. pmid:15620791
  8. 8. Stanton SJ, Schultheiss OC. The hormonal correlates of implicit power motivation. Journal of Research in Personality. 2009; 43(5): 942–949. pmid:20161646
  9. 9. Manning JT, Fink B. Digit Ratio (2D:4D), dominance, reproductive success, asymmetry, sociosexuality, and sexual orientation in the BBC internet study. American Journal of Human Biology. 2008; 20(4): 451–461. pmid:18433004
  10. 10. Maner JK, Miller SL, Coyle JM, Kaschak MP. Confronting intrasexual rivals. 2D:4D digit ratio predicts behavioral and endocrinological responses to infidelity threat. Social Psychological and Personality Science. 2014; 5(1): 119–128.
  11. 11. Hönekopp J, Schuster M. A meta-analysis on 2D: 4D and athletic prowess: substantial relationships but neither hand out-predicts the other. Personality and Individual Differences. 2010; 48(1): 4–10.
  12. 12. Moskowitz DS, Sutton R, Zuroff DC, Young SN. Fetal exposure to androgens, as indicated by digit ratios (2D: 4D), increases men’s agreeableness with women. Personality and Individual Differences. 2015; 75: 97–101.
  13. 13. McIntyre MH, Herrmann E, Wobber V, Halbwax M, Mohamba C, de Sousa N, et al. Bonobos have a more human-like second-to-fourth finger length ratio (2D: 4D) than chimpanzees: a hypothesized indication of lower prenatal androgens. Journal of Human Evolution. 2009; 56(4): 361–365. pmid:19285708
  14. 14. Nelson E, Shultz S. Finger length ratios (2D: 4D) in anthropoids implicate reduced prenatal androgens in social bonding. American Journal of Physical Anthropology. 2010; 141(3): 395–405. pmid:19862809
  15. 15. Nelson E, Hoffman CL, Gerald MS, Shultz S. Digit ratio (2D: 4D) and dominance rank in female rhesus macaques (Macaca mulatta). Behavioral ecology and sociobiology. 2010; 64(6): 1001–1009.
  16. 16. Roney JR, Whitham JC, Leoni M, Bellem A, Wielebnowski N, Maestripieri D. Relative digit lengths and testosterone levels in Guinea baboons. Hormones and behavior. 2004; 45(4): 285–290. pmid:15053945
  17. 17. Howlett C, Setchell JM, Hill RA, Barton RA. The 2D: 4D digit ratio and social behaviour in wild female chacma baboons (Papio ursinus) in relation to dominance, aggression, interest in infants, affiliation and heritability. Behavioral Ecology and Sociobiology. 2015; 69(1): 61–74.
  18. 18. Millet K. An interactionist perspective on the relation between 2D: 4D and behavior: An overview of (moderated) relationships between 2D: 4D and economic decision making. Personality and Individual Differences. 2011; 51(4): 397–401.
  19. 19. Longman D, Stock JT, Wells JCK. Digit ratio (2D: 4D) and rowing ergometer performance in males and females. American journal of physical anthropology. 2011; 144(3): 337–341. pmid:21302261
  20. 20. Manning JT, Morris L, Caswell N. Endurance running and digit ratio (2D: 4D): implications for fetal testosterone effects on running speed and vascular health. American Journal of Human Biology. 2007; 19(3): 416–421. pmid:17420996
  21. 21. Voracek M, Reimer B, Ertl C, Dressler SG. Digit ratio (2D: 4D), lateral preferences, and performance in fencing. Perceptual and Motor Skills. 2006; 103(2): 427–446. pmid:17165406
  22. 22. Coates JM, Gurnell M, Rustichini A. Second-to-fourth digit ratio predicts success among high-frequency financial traders. Proceedings of the National Academy of Sciences. 2009; 106(2): 623–628.
  23. 23. Hopp RN, de Moraes JP, Jorge J. Digit ratio and academic performance in dentistry students. Personality and Individual Differences. 2012; 52(5): 643–646.
  24. 24. Bosch-Domènech A, Brañas-Garza P, Espín AM. Can exposure to prenatal sex hormones (2D: 4D) predict cognitive reflection? Psychoneuroendocrinology. 2014; 43: 1–10. pmid:24703165
  25. 25. Brosnan M, Gallop V, Iftikhar N, Keogh E. Digit ratio (2D: 4D), academic performance in computer science and computer-related anxiety. Personality and Individual Differences, 2011; 51(4): 371–375.
  26. 26. van der Meij L, Almela M, Buunk AP, Dubbs S, Salvador A. 2D:4D in men is related to aggressive dominance but not to sociable dominance. Aggressive Behavior. 2012; 38(3): 208–212. pmid:22531996
  27. 27. Putz DA, Gaulin SJ, Sporter RJ, McBurney DH. Sex hormones and finger length: What does 2D: 4D indicate? Evolution and Human Behavior. 2004; 25(3): 182–199.
  28. 28. Vermeersch H, T’Sjoen G, Kaufman JM, Vincke J. 2D:4D, sex steroid hormones and human psychological sex differences. Hormones and Behavior. 2008; 54(2): 340–346. pmid:18440537
  29. 29. Hönekopp J, Watson S. Meta-analysis of digit ratio 2D: 4D shows greater sex difference in the right hand. American Journal of Human Biology. 2010; 22(5): 619–630. pmid:20737609
  30. 30. Manning J, Kilduff L, Cook C, Crewther B, Fink B. Digit ratio (2D: 4D): a biomarker for prenatal sex steroids and adult sex steroids in challenge situations. Frontiers in endocrinology. 2014; 5: 1–5. pmid:24523714
  31. 31. Millet K, Dewitte S. A subordinate status position increases the present value of financial resources for low 2D: 4D men. American Journal of Human Biology. 2008; 20(1): 110–115. pmid:17972318
  32. 32. Millet K, Dewitte S. The presence of aggression cues inverts the relation between digit ratio (2D: 4D) and prosocial behaviour in a dictator game. British Journal of Psychology. 2009; 100(1): 151–162.
  33. 33. Kilduff LP, Hopp RN, Cook CJ, Crewther BT, Manning JT. Digit ratio (2D: 4D), aggression, and testosterone in men exposed to an aggressive video stimulus. Evolutionary psychology. 2013; 11: 953–964. pmid:24113579
  34. 34. Ronay R, Galinsky AD. Lex talionis: Testosterone and the law of retaliation. Journal of Experimental Social Psychology. 2011; 47(3): 702–705.
  35. 35. Mehta PH, Josephs RA. Testosterone change after losing predicts the decision to compete again. Hormones and Behavior. 2006; 50(5): 684–692. pmid:16928375
  36. 36. Josephs RA, Mehta PH, Carre JM. Gender and social environment modulate the effects of testosterone on social behavior: comment on Eisenegger et al. Cogn. Sci. 2011; 14: 16–21.
  37. 37. Collias NE, Barfield RJ, Tarvyd ES. Testosterone versus psychological castration in the expression of dominance, territoriality and breeding behavior by male village weavers (Ploceus cucullatus). Behaviour. 2002; 139(6): 801–824.
  38. 38. Ruiz-de-la-Torre JL, Manteca X. Effects of testosterone on aggressive behaviour after social mixing in male lambs. Physiology & behavior. 1999; 68(1): 109–113.
  39. 39. Josephs RA, Sellers JG, Newman ML, Mehta PH. The mismatch effect: when testosterone and status are at odds. Journal of personality and social psychology. 2006; 90(6), 999–1013. pmid:16784348
  40. 40. Terburg D, Aarts H, van Honk J. Testosterone affects gaze aversion from angry faces outside of conscious awareness. Psychological science. 2012; 23: 459–463. pmid:22477106
  41. 41. Stirrat M, Perrett DI. Valid facial cues to cooperation and trust male facial width and trustworthiness. Psychological science. 2010; 21(3): 349–354. pmid:20424067
  42. 42. Stillman TF, Maner JK, Baumeister RF. A thin slice of violence: Distinguishing violent from nonviolent sex offenders at a glance. Evolution and Human Behavior. 2010; 31(4): 298–303.
  43. 43. Todorov A, Mandisodza AN, Goren A, Hall CC. Inferences of competence from faces predict election outcomes. Science. 2005; 308(5728): 1623–1626. pmid:15947187
  44. 44. Todorov A, Said CP, Engell AD, Oosterhof NN. Understanding evaluation of faces on social dimensions. Trends in cognitive sciences. 2008; 12(12): 455–460. pmid:18951830
  45. 45. Putman P, Hermans E, van Honk J. Emotional stroop performance for masked angry faces: it's BAS, not BIS. Emotion. 2004; 4(3): 305–311. pmid:15456399
  46. 46. Oosterhof NN, Todorov A. The functional basis of face evaluation. Proceedings of the National Academy of Sciences. 2008; 105(32): 11087–11092.
  47. 47. Windhager S, Schaefer K, Fink B. Geometric morphometrics of male facial shape in relation to physical strength and perceived attractiveness, dominance, and masculinity. American Journal of Human Biology. 2011;. 23(6): 805–814. pmid:21957062
  48. 48. Zebrowitz LA. Reading faces: Window to the soul? Boulder, CO: Westview Press; 1997.
  49. 49. Carré JM, McCormick CM, Mondloch CJ. Facial structure is a reliable cue of aggressive behavior. Psychological Science, 2009; 20(10): 1194–1198. pmid:19686297
  50. 50. Carré JM, McCormick CM. In your face: facial metrics predict aggressive behaviour in the laboratory and in varsity and professional hockey players. Proceedings of the Royal Society of London B: Biological Sciences. 2008(1651); 275: 2651–2656.
  51. 51. Stewart LH, Ajina S, Getov S, Bahrami B, Todorov A, Rees G. (2012). Unconscious evaluation of faces on social dimensions. Journal of Experimental Psychology: General. 2012; 141(4): 715–727.
  52. 52. Getov S, Kanai R, Bahrami B, Rees G. Human brain structure predicts individual differences in preconscious evaluation of facial dominance and trustworthiness. Social cognitive and affective neuroscience. 2015; 10(5): 690–699. pmid:25193945
  53. 53. Murphy RO, Ackermann KA, Handgraaf M. Measuring social value orientation. Judgment and Decision Making. 2011; 6(8): 771–781.
  54. 54. Todorov A, Dotsch R, Porter JM, Oosterhof NN, Falvello VB. Validation of data-driven computational models of social perception of faces. Emotion. 2013; 13(4): 724–738. pmid:23627724
  55. 55. Cogsdill EJ, Todorov AT, Spelke ES, Banaji MR. Inferring Character From Faces: A Developmental Study. Psychological science. 2014; 25(5): 1132–1139. pmid:24570261
  56. 56. FaceGen Modeller 3.2.; Singular Inversions Inc.; 2007. Demo version. Available:
  57. 57. Todorov A. Social Perception lab; 2013. Database: Dominancefaces. Available:
  58. 58. Goldberg LR. A broad-bandwidth, public domain, personality inventory measuring the lower-level facets of several five-factor models. In: Mervielde I, Deary I, De Fruyt F, Ostendorf F, editors. Personality psychology in Europe. Tilburg: Tilburg University Press; 1999. pp. 7–28.
  59. 59. De Bruine L. Facelab; 2004. AutoMetric software for measurement of 2D:4D ratios. Available:
  60. 60. Garbarino E, Slonim R, Sydnor J. Digit ratios (2D: 4D) as predictors of risky decision making for both sexes. Journal of Risk and Uncertainty. 2011; 42(1): 1–26.
  61. 61. Manning JT, Churchill AJG, Peters M. The Effects of Sex, Ethnicity, and Sexual orientation on Self-Measured Digit Ratio (2D:4D). Archives of Sexual Behavior. 2007; 36(2): 223–233. pmid:17373585
  62. 62. Fink B, Grammer K, Mitteroecker P, Gunz P, Schaefer K, Bookstein FL, Manning JT. Second to fourth digit ratio and face shape. Proceedings of the Royal Society of London B: Biological Sciences. 2005; 272(1576): 1995–2001.
  63. 63. Neave N, Laing S, Fink B, Manning JT. Second to fourth digit ratio, testosterone and perceived male dominance. Proceedings of the Royal Society of London B: Biological Sciences. 2003; 270(1529): 2167–2172.
  64. 64. Schaefer K, Mitteroecker P, Fink B, Bookstein FL. Psychomorphospace—from biology to perception, and back: towards an integrated quantification of facial form variation. Biological Theory. 2009.; 4(1):98–106.
  65. 65. Archer J. Testosterone and human aggression: an evaluation of the challenge hypothesis. Neuroscience & Biobehavioral Reviews. 2006; 30(3): 319–345.
  66. 66. Mazur A, Booth A. Testosterone and dominance in men. Behavioral and brain sciences. 1998; 21(03): 353–363.
  67. 67. Kilduff L, Cook C J, Bennett M, Crewther B, Bracken RM, Manning J. Right-left digit ratio (2D:4D) predicts free testosterone levels associated with a physical challenge. Journal of Sports Sciences. 2013; 31: 677–683. pmid:23210744
  68. 68. Crewther B, Cook C, Kilduff L, Manning J. Digit ratio (2D:4D) and salivarytestosterone, oetradiol and cortisol levels under challenge: Evidence for prenatal effects on adult endocrine responses. Early Human Development. 2015; 91(8): 451–456. pmid:26025335